Among fuel filler opening structures of automobiles, there are those in which a shutter is provided in an openable and closeable manner in the vicinity of a fuel filler opening through which a fuel filler nozzle can be inserted, and an annular operating ring is provided above the shutter. With this fuel filler opening structure for an automobile, when the fuel filler nozzle has been inserted through the fuel filler opening, the operating ring is enlarged in diameter by the inserted nozzle, and a lock on the shutter is released in conjunction with the enlarging of the operating ring.
With the lock on the shutter released, the fuel filler nozzle is inserted toward the shutter, whereby the shutter is pushed down and opened by the nozzle. There is a known technique whereby the fuel filler nozzle is inserted up to a fuel filling position while the shutter is in an opened state and fuel is supplied from the inserted nozzle to a fuel tank, as is disclosed in Patent Document 1, for example.
However, with the fuel filler opening structure of Patent Document 1, fuel could mistakenly be supplied from the fuel filler nozzle in a state in which the shutter has not been opened by the fuel filler nozzle. In this case, there is a danger that fuel supplied from the fuel filler nozzle will flow (backward) to the fuel filler opening, and the back-flowing fuel will strongly discharge to the outside from the fuel filler opening and come in contact with the user.
The fuel filler nozzle is commonly provided with a liquid level detection sensor in the distal end in the nozzle. When the liquid level of the fuel has risen to the liquid level detection sensor while the fuel is being supplied by the fuel filler nozzle, the liquid level of the fuel is detected by the liquid level detection sensor. When the liquid level of the fuel is detected by the liquid level detection sensor, the supply of fuel is stopped based on a detection signal of the sensor.
However, if the detection sensor fails, it becomes impossible for the liquid level of the fuel to be detected by the detection sensor and for the supply of fuel to be stopped. Therefore, the fuel supplied from the fuel filler nozzle flows back toward the fuel filler opening, the back-flowing fuel strongly discharges to the outside from the fuel filler opening, and the discharged fuel comes in contact with the user.